// Thread.js
// https://threadjs.deep-rain.com
// https://github.com/deep-rain/thread
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// Constants
var Type = {
  RESOLVE: 'resolve',
  NOTIFY: 'notify'
};
var REPLACE_SEQUENCE = '{{#CODE}}';
var CODE = 'onmessage = function(e){ postMessage({type:"' + Type.RESOLVE + '",content:({{#CODE}}).call(this, (e.data ? JSON.parse(e.data) : undefined))});};function notify(c){postMessage({type:"' + Type.NOTIFY + '", content:c})}';

var getEmbeddedCode = function (s) {
  return CODE.replace(REPLACE_SEQUENCE, s);
};

module.exports = (function () {

  // Deferred class
  var Deferred = function () {
    this.resolveQueues = [];
    this.rejectQueues = [];
    this.progressQueues = [];
    this.args = null;
    this.isDone = false;
    this.isFailed = false;
  };

  Deferred.prototype.done = function (func) {
    if (this.isDone) {
      func(this.args);
    } else {
      this.resolveQueues.push(func);
    }
    return this;
  };

  Deferred.prototype.fail = function (func) {
    if (this.isFailed) {
      func(this.args);
    } else {
      this.rejectQueues.push(func);
    }
    return this;
  };

  Deferred.prototype.always = function (func) {
    if (this.isFailed || this.isDone) {
      func(this.args);
    } else {
      this.resolveQueues.push(func);
      this.rejectQueues.push(func);
    }
    return this;
  };

  Deferred.prototype.progress = function (func) {
    this.progressQueues.push(func);
  };

  Deferred.prototype.resolve = function (obj) {
    this.isDone = true;
    this.args = obj;
    this.resolveQueues.forEach(function (q) {
      q(obj);
    });
    return this;
  };

  Deferred.prototype.notify = function (obj) {
    this.progressQueues.forEach(function (q) {
      q(obj);
    });
  };

  Deferred.prototype.reject = function (obj) {
    this.isFailed = true;
    this.args = obj;
    this.rejectQueues.forEach(function (q) {
      q(obj);
    });
    return this;
  };

  // Thread class
  var Thread = function (func, depends) {

    // check browser
    if (!window.Blob ||
      !window.URL ||
      !window.Worker) {
      throw new Error('this browser is not supported');
    }

    // inject dependent libraries.
    depends = depends || [];
    if (!(depends instanceof window.Array)) {
      depends = [depends];
    }

    var scripts = '';
    if (depends.length > 0) {
      scripts = 'importScripts("' + depends.join('','') + '");';
    }

    // create Blob object.
    var blob = new window.Blob([scripts + getEmbeddedCode(func.toString())]);
    this.blobUrl = window.URL.createObjectURL(blob);

    // greate Worker object.
    this.worker = new window.Worker(this.blobUrl);
    this.deferred = new Deferred();

    // add event listener.
    var self = this;

    // onmessage
    this.worker.addEventListener('message', function (e) {
      switch (e.data.type) {
      case Type.RESOLVE:
        self.deferred.resolve(e.data.content);
        return;
      case Type.NOTIFY:
        self.deferred.notify(e.data.content);
        return;
      }
    });

    // onerror
    this.worker.addEventListener('error', function (e) {
      self.deferred.reject(e);
    });
  };

  Thread.prototype.execute = function (obj) {
    if (this.isClosed) {
      throw new Error('thread has been closed.');
    }

    var json = JSON.stringify(obj);
    this.worker.postMessage(json);
    return this;
  };

  Thread.prototype.once = function (args) {
    var self = this;
    this.deferred.always(function () {
      self.terminate();
    });
    this.execute(args);
    this.isClosed = true;
    return this;
  };

  Thread.prototype.terminate = function () {
    window.URL.revokeObjectURL(this.blobUrl);
    this.worker.terminate();
    this.worker = null;
    this.deferred = null;
    this.blobUrl = null;
  };

  Thread.prototype.done = function (f) {
    this.deferred.done(f);
    return this;
  };

  Thread.prototype.fail = function (f) {
    this.deferred.fail(f);
    return this;
  };

  Thread.prototype.progress = function (f) {
    this.deferred.progress(f);
    return this;
  };

  return Thread;
})();
